Building core daylight illumination systems would facilitate illumination of the core regions of a building with sunlight, thus reducing electrical lighting requirements and improving lighting quality. Widespread usage of building core daylight illumination systems in the most common workplace environment—substantially open-plan, multi-story office buildings—could significantly reduce energy consumption and greenhouse gas emissions. To foster their widespread usage, building core daylight illumination systems must be cost-effective. A cost-effective sunlight redirector for a building core daylight illumination system is disclosed below.